<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
    <title>Document</title>
    <style>
        .b {
            border: 1px solid red;
        }
    </style>
</head>

<body>
    <a class="btn btn-default" href="#" role="button">Link</a>
    <button class="btn btn-primary" type="submit">Button</button>
    <input class="btn btn-warning" type="button" value="Input">
    <input class="btn btn-default" type="submit" value="Submit">
    <button type="button" class="btn btn-danger">（危险）Danger</button>
    <form>
        <div class="form-group">
            <label for="exampleInputEmail1">Email address</label>
            <input type="email" class="form-control" id="exampleInputEmail1" placeholder="Email">
        </div>
        <div class="form-group">
            <label for="exampleInputPassword1">Password</label>
            <input type="password" class="form-control" id="exampleInputPassword1" placeholder="Password">
        </div>

        <div class="checkbox">
            <label>
                <input type="checkbox"> Check me out
            </label>
        </div>
        <button type="submit" class="btn btn-default">Submit</button>
    </form>
    <ul class="dropdown-menu" aria-labelledby="dropdownMenuDivider">
        <li role="separator" class="divider"></li>

    </ul>
    <nav aria-label="Page navigation">
        <ul class="pagination">
            <li>
                <a href="#" aria-label="Previous">
                    <span aria-hidden="true">&laquo;</span>
                </a>
            </li>
            <li><a href="#">1</a></li>
            <li><a href="#">2</a></li>
            <li><a href="#">3</a></li>
            <li><a href="#">4</a></li>
            <li><a href="#">5</a></li>
            <li>
                <a href="#" aria-label="Next">
                    <span aria-hidden="true">&raquo;</span>
                </a>
            </li>
        </ul>
    </nav>
    <div class="row">
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
        <div class="col-md-1 b">.col-md-1</div>
    </div> b
    <div class="row">
        <div class="col-md-8 b">.col-md-8</div>
        <div class="col-md-4 b">.col-md-4</div>
    </div>
    <div class="row">
        <div class="col-md-4 b">.col-md-4</div>
        <div class="col-md-4 b">.col-md-4</div>
        <div class="col-md-4 b">.col-md-4</div>
    </div>
    <div class="row">
        <div class="col-md-6 col-sm-3 b">.col-md-6</div>
        <div class="col-md-6  col-sm-3 b">.col-md-6</div>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</body>

</html>